Propaganda was initially employed as an effort to raise public health awareness and for various other attempts to influence the public to support one cause or another. It soon became a tool of war, as governments used detailed images and persuasive words to urge citizens to do their part to aid war efforts. During World War II, the Allies spent a considerable amount of time using propaganda to promote enlistment, war bonds, rationing, "victory" gardens, safe sex and patriotism on the home fronts.
These are some of the best, most creative and/or witty propaganda I've come across in my time as a History major:
And this is not propaganda, but I saw it in a WWII class a few months ago, and I LOVE it: